The present invention is directed to a measuring tip unit for contacting planar microwave circuits.
Measurement tip units for microwave wafer measurement means or wafer probes, which units have a coaxial cable that leads to a measuring apparatus for example to a vectorial network analyzer in contact with a contact tip, are disclosed by U.S. Pat. No. 4,871,964, whose disclosure is incorporated by reference, and by the Sales Brochure for GGB Industries, Inc. for the "PicoProbe".RTM. which is a high performance microwave probe. The inner conductor of the coaxial cable extends beyond the outer conductor and is pointed at the end and bent downward in the shape of a claw. A contact spring, also bent downward in a claw shape, is fastened to the outer conductor of the coaxial cable on at least one side. These known measurement tips wear out relatively quickly during use, for example, within months and there is also the danger of breakage of the measurement tip due to faulty control during placement. The entire measuring tip unit must then be exchanged and replaced.
Similar considerations hold for another known measurement tip unit in which the measuring tip is constructed in a coplanar line technology and is disclosed in U.S. Pat. No. 4,849,689, whose disclosure is incorporated by reference thereto and which was the basis for European Letters Patent 0 367 542. The actual measurement tip consists of a triangular dielectric substrate on whose back surface a coplanar line is fashioned. The substrate bearing the coplanar line is relatively sensitive to wear and breakage. During the adjustment of the measuring tip unit under a microscope, the measuring point is covered over a relative large surface by the substrate, and only the ends of the coplanar lines are visible. Therefore, adjustment is thus very difficult and imprecise.